Loop antenna



June 12, 1928.

F. A. KOLSTER LOOP ANTENNA Filed Sept. 8, 1926 2 Sheets-Sheet l FIE J June 12, 1928. 1,673,249

F. A. KoLsTER LOOP ANTENNA Filed sept. 8. 192s 2 sheets-sneer 2 E 'IIE E ze v A 1ro/uns Patented June 12, 1928.

UNITED STATES PATENT OFFICE.

FREDERICK A. KOLSTER, OF PALO ALTO, CALIFORNIA, ASSIGNOR TO FEDERAL TELE- GRAPH COMPANY, 0F SAN FRANCISCO, CALIFORNIA, A CORPORATION OF CALI- FORNIA.

LOOP ANTENNA.

Application led September 8, 1926. Serial lo. 134,216,

This invention relates generally to antennac for elfecting a transfer of radio energy between an electrical circuit and an absorption medium.

In directive radio reception such as einployed in radio compas systems, it is common practice to make use of antennae comprisino' a lumped inductance which ma b e rotated to bring its plane in any desire direction. In making radio compass installa tions upon ships, the loop antenna is placed in an exposed position where it is subJected to severe climatic conditions. Such antennae must have not only high electrical eliiciency but must be impervious to moisture and have great mechanical strength.

It is an object of this invention to devise f an encased or shielded loop antenna which will have ihigh mechanical strength and low wind resistance.

It is a further object of this invention to devise a loop antenna which will be inclosed in a metal shield or casing b ut which will have hi h electrical elliciency.

Further o jects of this invention will appear from the followinv description in which I have set forth t e preferred embodiment of my invention. It is to be understood that various modifications may be made within the scope of the appended claims and within a range of equivalents consistent with the prior art.

Referring to the drawings:

Figure 1 is a side elevational view showing a loop antenna constructed in accordance with this invention.

Fig. 2 is a detail showin a modification of the invention shown in ig. 1.

Fig. 3 is a diagrammatical view illustrat ing the electrical connections to the loop conductors andr metal casing.

The invention comprises enerally la metal shield or casin constructe in the form of a fiat loop an within which one or more antenna conductors are wound. The ends of the metal casing are insulated from direct electrical contact with each other and are electrically associated with they antenna conductor so that the casing forms a part of the antenna inductance. Thus referring to the drawings there is shown a hollow metal casing 10 which is bent in the form of a relatively flat loop. This casing ma be constructed of any suitable materia having high electrical conductivity such as copper, and is preferably tubular in shape. The ends 11 and 12 of the casing are preferabl insulated .from direct electrical contact lWit i each other as b means of a sleeve 13 of insulating material. For rotatably supporting the casing in a vertical plane, the tube has been shown as mounted upon a hollow shaft 14,*this shaft being journaled within a suitable bearingl. 'llie ends 11 and 12 of the casing are preferably arranged so that they are disposed symmetrical with respect to the axis of rotation 16.

In order .to form the antenna inductance, one or more conductors are wound within the continuous passageway 18 provided by the interior of the casing 10. Thus there is shown an insulated conductor 19 which 1 s looped a number of times within the cas ing 10, the terminals 20 being extended through the hollow shaft 14 for making connection with a receiving or signaling circuit. While the arrangement so' far described would operate as an antenna, its electrical efficiency would be impaired by the presence .of the metal casing 10. In order to increase the electrical efficiency the metal casing 10 is made a part of the antenna inductance. Thus one of the intermediate turns ofthe conductor 19 is interrupted and the metal casing 10 inserted in series with the same so that the casing forms one loop of the antenna inductance. These electrical connections to the metal casing 10 have been indicated at 21 and 22 and are preferably made adjacent the ends lof the casing.

A sligh t1 shown in 2 in'which the ends of the metal casin 10 have been positioned at the bottom of t e loop, as for example by incorporating it in the mounting of the casing upon the rotatable shaft 14. In this case the ends of the casing 10 are shown as mounted within an insulating sleeve or block 25 which is secured to the rotatable shaft 14. As in' the case of the loop previously described the casing is inserted 1n series with the antenna inductance as indicated by the electrical connections 21 and 22.

In Fig. 3 the electrical connections of the antenna have been illustrated diagrammatically. As indicated, the loops or turns of the antenna conductor 19 upon either side of the series connection with the casing 10 are preferably equal so that the casing forms the central portion of the antenna inductance. The casing may also be rounded intermediate its ends as indicate at 28. The v terminal wires 20 are connected with the electrical apparatus commonly associated with such antenn as is well known in the radio art. Suitable means such as a variable condenser 29 is generally shunted across the loop in order to bring the same in resonance to the desired signal frequency. The antenna is of course directional in the direction of the lane of the loop.

Whi e the device has been 'described with reference to radio Compasses, it is of course applicable for use in other radio systems, both for reception and transmission of radio energy. The metal casing serves to provide a ruged frame work having a minimum of win resistance and which effectively protects the antenna conductor against climatic conditions.

I claim:

1. An antenna of the class described comprising an elongated metal casing in the form of a loop, the ends of said casing being insulated from direct electrical contact with each other, and conductors looped within said easing to form an inductance.

2. An antenna of the class described 'comrising an elongated metal casing in the orm of a loop, and a conductor wound within said casing to form aninductance, said conductor being electrically connected with -the casing whereby the casing is incorporated as one loop of the inductance.

l 3. An antenna of the class described com- Wrisingl an elongated metal casing in the form of a loop, and a conductor wound withinsaid casing to form an inductance, an intermediate portion of said conductor being electrically connected with the casing whereby the casing forms an intermediate loop of said inductance.

4. Anantenna of the class described comprising a tubular metal casing in the form of a fiat loop, the ends of said loop being insulated from direct electrical contact with each other, an insulated conductor wound within the interior of the'casing to form an inductance, the intermediate portion of the conductor being electricallyT connected in series with said casing whereby the casing forms one of the intermediate turns of the inductance, and means for rotatably supporting said casing.

5. An antenna yof the class describedcomf m hand.l

y FREDERICK A. KOLSTER. 

